Mesias Pedroza

Blockade of IL-6 Trans Signaling Attenuates Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a lethal lung disease with progressive fibrosis and death within 2–3 y of diagnosis. IPF incidence and prevalence rates are increasing annually with few effective treatments available. Inhibition of IL-6 results in the attenuation of pulmonary fibrosis in mice. It is unclear whether this is due to blockade of classical signaling, mediated by membrane-bound IL-6Rα, or trans signaling, mediated by soluble IL-6Rα (sIL-6Rα). Our study assessed the role of sIL-6Rα in IPF. We demonstrated elevations of sIL-6Rα in IPF patients and in mice during the onset and progression of fibrosis. We demonstrated that protease-mediated cleavage from lung macrophages was important in production of sIL-6Rα. In vivo neutralization of sIL-6Rα attenuated pulmonary fibrosis in mice as seen by reductions in myofibroblasts, fibronectin, and collagen in the lung. In vitro activation of IL-6 trans signaling enhanced fibroblast proliferation and extracellular matrix protein production, effects relevant in the progression of pulmonary fibrosis. Taken together, these findings demonstrate that the production of sIL-6Rα from macrophages in the diseased lung contributes to IL-6 trans signaling that in turn influences events crucial in pulmonary fibrosis.

Distinct Roles for the A2B Adenosine Receptor in Acute and Chronic Stages of Bleomycin-Induced Lung Injury

Adenosine is an extracellular signaling molecule that is generated in response to cell injury where it orchestrates tissue protection and repair. Whereas adenosine is best known for promoting anti-inflammatory activities during acute injury responses, prolonged elevations can enhance destructive tissue remodeling processes associated with chronic disease states. The generation of adenosine and the subsequent activation of the adenosine 2B receptor (A2BR) is an important processes in the regulation of both acute and chronic lung disease. The goal of this study was to examine the contribution of the A2BR in models of bleomycin-induced lung injury that exhibit varying degrees of acute and chronic injury. Intratracheal bleomycin exposure results in substantial acute lung injury followed by progressive fibrosis. In this model, genetic removal of the A2BR resulted in enhanced loss of barrier function and increased pulmonary inflammation, with few differences in indexes of pulmonary fibrosis. These results support an anti-inflammatory role for this receptor in this model of acute lung injury. In contrast, systemic exposure of mice to bleomycin resulted in modest acute lung injury together with progressive pulmonary fibrosis. In this model, the effects of A2BR removal on acute lung injury were negligible; however, there were substantial reductions in pulmonary fibrosis, supporting a profibrotic role for this receptor. A2BR-dependent regulation of IL-6 production was identified as a potential mechanism involved in the diminished pulmonary fibrosis seen in A2BR knockout mice exposed to i.p. bleomycin. These studies highlight the distinct roles of A2BR signaling during acute and chronic stages of lung injury.

Interleukin-6 Contributes to Inflammation and Remodeling in a Model of Adenosine Mediated Lung Injury

Background Chronic lung diseases are the third leading cause of death in the United States due in part to an incomplete understanding of pathways that govern the progressive tissue remodeling that occurs in these disorders. Adenosine is elevated in the lungs of animal models and humans with chronic lung disease where it promotes air-space destruction and fibrosis. Adenosine signaling increases the production of the pro-fibrotic cytokine interleukin-6 (IL-6). Based on these observations, we hypothesized that IL-6 signaling contributes to tissue destruction and remodeling in a model of chronic lung disease where adenosine levels are elevated. Methodology/Principal Findings We tested this hypothesis by neutralizing or genetically removing IL-6 in adenosine deaminase (ADA)-deficient mice that develop adenosine dependent pulmonary inflammation and remodeling. Results demonstrated that both pharmacologic blockade and genetic removal of IL-6 attenuated pulmonary inflammation, remodeling and fibrosis in this model. The pursuit of mechanisms involved revealed adenosine and IL-6 dependent activation of STAT-3 in airway epithelial cells. Conclusions/Significance These findings demonstrate that adenosine enhances IL-6 signaling pathways to promote aspects of chronic lung disease. This suggests that blocking IL-6 signaling during chronic stages of disease may provide benefit in halting remodeling processes such as fibrosis and air-space destruction.

STAT-3 contributes to pulmonary fibrosis through epithelial injury and fibroblast-myofibroblast differentiation

Lung fibrosis is the hallmark of the interstitial lung diseases. Alveolar epithelial cell (AEC) injury is akey step that contributes to a profibrotic microenvironment. Fibroblasts and myofibroblasts subsequently accumulate and deposit excessive extracellular matrix. In addition to TGF‐β, the IL‐6 family of cytokines, which signal through STAT‐3, may also contribute to lung fibrosis. In the current manuscript, the extent to which STAT‐3 inhibition decreases lung fibrosis is investigated. Phosphorylated STAT‐3 was elevated in lung biopsies from patients with idiopathic pulmonary fibrosis and bleomycin (BLM)‐induced fibrotic murine lungs. C‐188‐9, a small molecule STAT‐3 inhibitor, decreased pulmonary fibrosis in the intraperitoneal BLM model as assessed by arterial oxygen saturation (control, 84.4 ± 1.3%; C‐188‐9, 94.4 ± 0.8%), histology (Ashcroft score: untreated, 5.4 ± 0.25; C‐188‐9, 3.3 ± 0.14), and attenuated fibrotic markers such as diminished α‐smooth muscle actin, reduced collagen deposition. In addition, C‐188‐9 decreased the expression of epithelial injury markers, including hypoxia‐inducible factor‐1α (HIF‐1α) and plasminogen activator inhibitor‐1 (PAI‐1). In vitro studies show that inhibition of STAT‐3 decreased IL‐6‐ and TGF‐β‐induced expression of multiple genes, including HIF‐1α and PAI‐1, in AECs. Furthermore, C‐188‐9 decreased fibroblast‐to‐myofibroblast differentiation. Finally, TGF‐β stimulation of lung fibroblasts resulted in SMAD2/SMAD3‐dependent phosphorylation of STAT‐3. These findings demonstrate that STAT‐3 contributes to the development of lung fibrosis and suggest that STAT‐3 may be a therapeutic target in pulmonary fibrosis.—Pedroza, M., Le, T. T., Lewis, K., Karmouty‐Quintana, H., To, S., George, A. T., Blackburn, M. R., Tweardy, D. J., Agarwal, S. K. STAT‐3 contributes to pulmonary fibrosis through epithelial injury and fibroblast‐myofibroblast differentiation. FASEB J. 30, 129‐140 (2016). www.fasebj.org

Adenosine A2B receptor and hyaluronan modulate pulmonary hypertension associated with Chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death worldwide. The development of pulmonary hypertension (PH) in patients with COPD is strongly associated with increased mortality. Chronic inflammation and changes to the lung extracellular matrix (ECM) have been implicated in the pathogenesis of COPD, yet the mechanisms that lead to PH secondary to COPD remain unknown. Our experiments using human lung tissue show increased expression levels of the adenosine A2B receptor (ADORA2B) and a heightened deposition of hyaluronan (HA; a component of the ECM) in remodeled vessels of patients with PH associated with COPD. We also demonstrate that the expression of HA synthase 2 correlates with mean pulmonary arterial pressures in patients with COPD, with and without a secondary diagnosis of PH. Using an animal model of airspace enlargement and PH, we show that the blockade of ADORA2B is able to attenuate the development of a PH phenotype that correlates with reduced levels of HA deposition in the vessels and the down-regulation of genes involved in the synthesis of HA.

Identification of Cadherin 11 as a Mediator of Dermal Fibrosis and Possible Role in Systemic Sclerosis

Systemic sclerosis (SSc) is a chronic autoimmune disease clinically manifesting as progressive fibrosis of the skin and internal organs. Recent microarray studies demonstrated that cadherin 11 (Cad‐11) expression is increased in the affected skin of patients with SSc. The purpose of this study was to examine our hypothesis that Cad‐11 is a mediator of dermal fibrosis.

Mitotic Centromere-associated Kinesin (MCAK) Mediates Paclitaxel Resistance

Background: Mutations causing paclitaxel resistance stimulate microtubule detachment from centrosomes. Results: Depletion of mitotic centromere-associated kinesin (MCAK) reverses microtubule detachment and paclitaxel resistance. Conclusion: MCAK plays a pivotal role in the mechanism of microtubule detachment and drug resistance. Significance: The ability of MCAK to reverse paclitaxel resistance identifies modulators of microtubule detachment as important new drug targets. Paclitaxel has powerful anticancer activity, but some tumors are inherently resistant to the drug, whereas others are initially sensitive but acquire resistance during treatment. To deal with this problem, it will be necessary to understand the mechanisms of drug action and resistance. Recent studies indicate that paclitaxel blocks cell division by inhibiting the detachment of microtubules from centrosomes. Here, we demonstrate that mitotic centromere-associated kinesin (MCAK), a kinesin-related protein that destabilizes microtubules, plays an important role in microtubule detachment. Depletion of MCAK altered mitotic spindle morphology, increased the frequency of lagging chromosomes, and inhibited the proliferation of WT CHO cells, confirming that it is an essential protein for cell division. In contrast, MCAK depletion rescued the proliferation of mutant paclitaxel-dependent cell lines that are unable to divide because of defective spindle function resulting from altered α-tubulin or class III β-tubulin overexpression. In concert with the correction of mitotic defects, loss of MCAK reversed an aberrantly high frequency of microtubule detachment in the mutant cells and increased their sensitivity to paclitaxel. The results indicate that MCAK affects cell sensitivity to mitotic inhibitors by modulating the frequency of microtubule detachment, and they demonstrate that changes in a microtubule-interacting protein can reverse the effects of mutant tubulin expression.

Sustained adenosine exposure causes lung endothelial apoptosis: a possible contributor to cigarette smoke-induced endothelial apoptosis and lung injury

Pulmonary endothelial cell (EC) apoptosis has been implicated in the pathogenesis of emphysema. Cigarette smoke (CS) causes lung EC apoptosis and emphysema. In this study, we show that CS exposure increased lung tissue adenosine levels in mice, an effect associated with increased lung EC apoptosis and the development of emphysema. Adenosine has a protective effect against apoptosis via adenosine receptor-mediated signaling. However, sustained elevated adenosine increases alveolar cell apoptosis in adenosine deaminase-deficient mice. We established an in vitro model of sustained adenosine exposure by incubating lung EC with adenosine in the presence of an adenosine deaminase inhibitor, deoxycoformicin. We demonstrated that sustained adenosine exposure caused lung EC apoptosis via nucleoside transporter-facilitated intracellular adenosine uptake, subsequent activation of p38 and JNK in mitochondria, and ultimately mitochondrial defects and activation of the mitochondria-mediated intrinsic pathway of apoptosis. Our results suggest that sustained elevated adenosine may contribute to CS-induced lung EC apoptosis and emphysema. Our data also reconcile the paradoxical effects of adenosine on apoptosis, demonstrating that prolonged exposure causes apoptosis via nucleoside transporter-mediated intracellular adenosine signaling, whereas acute exposure protects against apoptosis via activation of adenosine receptors. Inhibition of adenosine uptake may become a new therapeutic target in treatment of CS-induced lung diseases.

Hypoxia-induced deoxycytidine kinase expression contributes to apoptosis in chronic lung disease

Chronic obstructive pulmonary disease (COPD) is characterized by persistent inflammation and tissue remodeling and is a leading cause of death in the United States. Increased apoptosis of pulmonary epithelial cells is thought to play a role in COPD development and progression. Identification of signaling pathways resulting in increased apoptosis in COPD can be used in the development of novel therapeutic interventions. Deoxyadenosine (dAdo) is a DNA breakdown product that amplifies lymphocyte apoptosis by being phosphorylated to deoxyadenosine triphosphate (dATP). dAdo is maintained at low levels by adenosine deaminase (ADA). This study demonstrated that mice lacking ADA developed COPD manifestations in association with elevated dAdo and dATP levels and increased apoptosis in the lung. Deoxycitidine kinase (DCK), a major enzyme for dAdo phosphorylation, was up‐regulated in mouse and human airway epithelial cells in association with air‐space enlargement. Hypoxia was identified as a novel regulator of DCK, and inhibition of DCK resulted in diminished dAdo‐mediated apoptosis in the lungs. Our results suggest that activating the dAdo‐DCK‐dATP pathway directly results in increased apoptosis in the lungs of mice with air‐space enlargement and suggests a novel therapeutic target for the treatment of COPD.—Weng, T., Karmouty‐Quintana, H., Garcia‐Morales, L. J., Molina, J. G., Pedroza, M., Bunge, R. R., Bruckner, B. A., Loebe, M., Seethamraju, H., and Blackburn, M. R. Hypoxia‐induced deoxycytidine kinase expression contributes to apoptosis in chronic lung disease. FASEB J. 27, 2013–2026 (2013). www.fasebj.org

Sustained Adenosine Exposure Causes Lung Endothelial Barrier Dysfunction via Nucleoside Transporter–Mediated Signaling

Previous studies by our group as well as others have shown that acute adenosine exposure enhances lung vascular endothelial barrier integrity and protects against increased permeability lung edema. In contrast, there is growing evidence that sustained adenosine exposure has detrimental effects on the lungs, including lung edema. It is well established that adenosine modulates lung inflammation. However, little is known concerning the effect of sustained adenosine exposure on lung endothelial cells (ECs), which are critical to the maintenance of the alveolar-capillary barrier. We show that exogenous adenosine plus adenosine deaminase inhibitor caused sustained elevation of adenosine in lung ECs. This sustained adenosine exposure decreased EC barrier function, elevated cellular reactive oxygen species levels, and activated p38, JNK, and RhoA. Inhibition of equilibrative nucleoside transporters (ENTs) prevented sustained adenosine-induced p38 and JNK activation and EC barrier dysfunction. Inhibition of p38, JNK, or RhoA also partially attenuated sustained adenosine-induced EC barrier dysfunction. These data indicate that sustained adenosine exposure causes lung EC barrier dysfunction via ENT-dependent intracellular adenosine uptake and subsequent activation of p38, JNK, and RhoA. The antioxidant N-acetylcysteine and the NADPH inhibitor partially blunted sustained adenosine-induced JNK activation but were ineffective in attenuation of p38 activation or barrier dysfunction. p38 was activated exclusively in mitochondria, whereas JNK was activated in mitochondria and cytoplasm by sustained adenosine exposure. Our data further suggest that sustained adenosine exposure may cause mitochondrial oxidative stress, leading to activation of p38, JNK, and RhoA in mitochondria and resulting in EC barrier dysfunction.